Downloaded from https://www.everyspec.com STRUCTURES developing at each point in the material. Figure 2-2 illustrates the separate effects Imagine that parallel planes are passed of normal and shear strains on the deforma- through two neighboring points. The normal tion of a square element of the material. In strain is the relative displacements of these part (a) of the figure, the element is sub- points normal to the planes divided by the jected only to normai strains. This type of original distance between the planes.
The deformation would occur, for example, if a shear slrain is defined as the relative dis- normal stress in the x direction were the only "placement of the two points measured paral- stress acting an the element, .11vie that a lel to the planes, divided by the original strain in the y direction accompanies the distance between the planes. Normal strains strain in the x direction due to stress in the have the effect of distorting a cubical element x direction.
Part (b) of the figure illustrates of t.e material without altering the ortho- the manner in which the element would be gonality between tie sides of the element, distorted if it were subjected to a condition whereas shearing trains are a measure of of pure shear stresses. In the most general the change from the original right angles case there would also be u displacements between the side-. (x-direction) of the end points of the element. B YL MAXIMUM STRESS iW A ] 1 YIELD STRESS /-PROPORTIONAL U IT 0 I c STRAIN ALUMINUM ALLOYS VEELD STRESS 7 MAXIMUM STRESS UJ 'ROPOW'1ONAL LIMIT a: // ,STRAIN STEELS FiSu.,e 2-1. Typical Tensile Stjss-Strnin Dogrumzl for Steel and Alum'nuzi Alloys 8